A supercritical carbon dioxide power generation unit with the function of self-removing water from the working fluid

Abstract

The present invention discloses a supercritical carbon dioxide power generation unit with a working medium self-dehydration function, which includes a pressure stabilizing tank, a compressor, a recuperator, a boiler, a turbine generator set, a precooler, a cooling fan, a thick-tube cooler, a thin-tube refrigerator and a drain pipe; the outlet of the pressure stabilizing tank is divided into two paths after passing through the compressor, one of which is connected to the inlet of the boiler through the heat absorption side of the recuperator, the outlet of the boiler is connected to the inlet of the turbine generator set, the exhaust port of the turbine generator set is connected to the inlet of the precooler through the heat release side of the recuperator, the outlet of the precooler is connected to the inlet of the pressure stabilizing tank, and the other path is connected to the drain pipe through the thick-tube cooler and the thin-tube refrigerator. The thin-tube refrigerator is located in the pressure stabilizing tank, and a liquid discharge port is arranged at the bottom of the pressure stabilizing tank. The cooling fan is facing the thick-tube cooler. This unit can solve the problem of carbonic acid corrosion of metal materials caused by the mixture of carbon dioxide and water vapor at high temperatures.

Description

Technical Field

[0001] The present invention relates to a supercritical carbon dioxide power generation unit, and more particularly to a supercritical carbon dioxide power generation unit with a working medium self-dewatering function. Background Art

[0002] The supercritical carbon dioxide (S-CO 2 ) power generation system is a Brayton cycle system using supercritical CO 2 as the working medium. Its cycle process is as follows: First, S-CO 2 is boosted in pressure by a compressor; then, the S-CO 2 working medium is isobarically heated by an external heat source heater (boiler); secondly, the working medium enters a turbine to drive the turbine to do work, and the turbine drives an electric generator to generate electricity; finally, the S-CO 2 working medium enters a cooler to return to the initial state and then enters the compressor to form a closed cycle.

[0003] Carbon dioxide has a very unique physical property: when the temperature reaches 30.98 °C and the pressure reaches 7.38 MPa (i.e., the critical point of CO 2 ), its physical state is between liquid and gas, the density is close to that of a liquid, the viscosity is close to that of a gas, and the diffusion coefficient is about 100 times that of a liquid. This state is called the "supercritical" state. Carbon dioxide in the supercritical state has a density greater than that of a gas and a viscosity smaller than that of a liquid, and has characteristics such as strong fluidity, high heat transfer efficiency, and small compressibility. Compared with the critical value of water at 373.95 °C / 22.04 MPa, a lower energy consumption can make CO 2 reach the critical state. Using it as the circulating working medium, the power generation efficiency of a thermal power unit is expected to exceed 50%, and this power generation technology has a very bright application prospect.

[0004] Currently, the supercritical carbon dioxide cycle power generation technology has been theoretically verified on a KW-level small test bench and optimization and improvement work has been carried out, while larger-scale MW-level practical units have entered the actual construction stage. Some problems that did not occur on the small test bench began to emerge on the MW-level test units, and the metal corrosion of pipes is one of the more important problems. Through comparative experiments, some researchers have obtained that the degree of oxidation corrosion of metal pipes by high-temperature CO 2 gas is lower than that of water vapor. In fact, due to the influence of hydrostatic tests, chemical cleaning, and wet rainy seasons on the on-site units, moisture will inevitably remain in the internal pipes, and carbon dioxide boilers usually do not have drain valves, which will cause the filled CO 2The gas will mix with water vapor at high temperatures to form "carbonic acid vapor". Although carbonic acid is a weak acid, the rate of the "acid corrosion" reaction greatly accelerates at high temperatures above 500°C, still posing a huge threat to the safety of metal materials. At a certain construction site, after the supercritical carbon dioxide unit was heated up and pressurized during boiler ignition, problems such as the failure and leakage of metal spiral gaskets occurred at multiple flange connections in a short period of time, causing great safety risks to personnel and equipment. Thus, the "carbonic acid corrosion" problem of supercritical carbon dioxide units must be taken seriously enough.

[0005] If a water removal device can be set at the low-temperature and low-pressure part of this closed cycle and regularly opened during the operation of the unit to remove the moisture in the working medium, the "carbonic acid corrosion" risk faced by pipes, metal gaskets, etc. can be greatly reduced. The system composition of the supercritical carbon dioxide unit is as Figure 2 shown. The lowest temperature and pressure part of the system is the pressure stabilizing tank. The pressure stabilizing tank is a gas storage tank with a relatively large capacity, providing gas source for the downstream compressor. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a supercritical carbon dioxide power generation unit with the function of self-removing water from the working medium, which can solve the problem of carbonic acid corrosion of metal materials caused by the mixture of carbon dioxide and water vapor at high temperatures.

[0007] To achieve the above purpose, the supercritical carbon dioxide power generation unit with the function of self-removing water from the working medium described in the present invention includes a pressure stabilizing tank, a compressor, a recuperator, a boiler, a turbine generator set, a pre-cooler, a cooling fan, a thick tube cooler, a thin tube refrigerator, and an exhaust pipe;

[0008] The outlet of the pressure stabilizing tank is divided into two paths after passing through the compressor. One path is connected to the inlet of the boiler through the heat absorption side of the recuperator, the outlet of the boiler is connected to the inlet of the turbine generator set, the exhaust port of the turbine generator set is connected to the inlet of the pre-cooler through the heat release side of the recuperator, the outlet of the pre-cooler is connected to the inlet of the pressure stabilizing tank, and the other path is connected to the exhaust pipe through the thick tube cooler and the thin tube refrigerator. The thin tube refrigerator is located inside the pressure stabilizing tank, a drain port is provided at the bottom of the pressure stabilizing tank, and the cooling fan is facing the thick tube cooler.

[0009] The thick tube cooler is connected to the exhaust pipe through a throttle valve and the thin tube refrigerator.

[0010] A drain valve is provided at the drain port.

[0011] The compressor is a centrifugal compressor.

[0012] The recuperator is a printed circuit board heat exchanger.

[0013] The pre-cooler is a printed circuit board heat exchanger.

[0014] The throttle valve is an electric control valve.

[0015] Both the thin-tube cooler and the thick-tube cooler are formed by winding steel pipes.

[0016] The present invention has the following beneficial effects:

[0017] When the supercritical carbon dioxide power generation unit with the function of self-removing water of the working medium is specifically operated, the low-temperature carbon dioxide gas output from the pressure stabilizing tank is pressurized by the compressor and then enters the regenerator, and in the regenerator, it exchanges heat with the higher-temperature exhaust gas output from the turbine power generation unit to increase the temperature, and then enters the boiler to absorb heat and increase the temperature to the rated parameters. The carbon dioxide output from the boiler enters the turbine power generation unit to expand and do work. The exhaust gas discharged from the turbine power generation unit enters the regenerator to exchange heat and reduce the temperature, then enters the precooler to be cooled, and then enters the pressure stabilizing tank, and exchanges heat with the low-temperature medium in the thin-tube cooler to reduce the temperature, so that the temperature of the gas in the pressure stabilizing tank is reduced, and the water vapor in the gas condenses into liquid droplets and gradually drips to the bottom of the pressure stabilizing tank to reduce the humidity in the gas, and solve the problem of carbonic acid corrosion of metal materials caused by the mixture of carbon dioxide and water vapor at high temperatures. Description of the Drawings

[0018] Figure 1 is a schematic structural diagram of the present invention;

[0019] Figure 2 is a schematic structural diagram of the prior art.

[0020] Among them, 1 is the pressure stabilizing tank, 2 is the compressor, 3 is the regenerator, 4 is the boiler, 5 is the turbine power generation unit, 6 is the precooler, 7 is the cooling fan, 8 is the thick-tube cooler, 9 is the throttle valve, 10 is the thin-tube cooler, 11 is the drain valve, and 12 is the vent pipe. Detailed Embodiments

[0021] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments, and are not intended to limit the scope of the present invention disclosure. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessarily confusing the concepts disclosed in the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0022] The structural schematic diagrams according to the disclosed embodiments of the present invention are shown in the accompanying drawings. These figures are not drawn to scale, where for the purpose of clear expression, some details are enlarged and some details may be omitted. The shapes of various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in actuality due to manufacturing tolerances or technical limitations. Those skilled in the art can additionally design regions / layers with different shapes, sizes, and relative positions according to actual requirements.

[0023] Referring Figure 1 , the supercritical carbon dioxide power generation unit with the function of self-dehydrating the working medium according to the present invention includes a pressure stabilizing tank 1, a compressor 2, a recuperator 3, a boiler 4, a turbine generator set 5, a precooler 6, a cooling fan 7, a thick-tube cooler 8, a throttle valve 9, a thin-tube refrigerator 10, a drain valve 11, and a vent pipe 12;

[0024] The outlet of the pressure stabilizing tank 1 is divided into two paths after passing through the compressor 2. One path is connected to the inlet of the boiler 4 through the heat absorption side of the recuperator 3. The outlet of the boiler 4 is connected to the inlet of the turbine generator set 5. The exhaust port of the turbine generator set 5 is connected to the inlet of the precooler 6 through the heat release side of the recuperator 3. The outlet of the precooler 6 is connected to the inlet of the pressure stabilizing tank 1. The other path is connected to the vent pipe 12 through the thick-tube cooler 8, the throttle valve 9, and the thin-tube refrigerator 10. The thin-tube refrigerator 10 is located inside the pressure stabilizing tank 1. A liquid discharge port is provided at the bottom of the pressure stabilizing tank 1, and a drain valve 11 is provided at the liquid discharge port. The cooling fan 7 is directly opposite to the thick-tube cooler 8.

[0025] The compressor 2 is a centrifugal compressor; the recuperator 3 is a printed circuit board heat exchanger; the precooler 6 is a printed circuit board heat exchanger; the throttle valve 9 is an electric control valve.

[0026] The working process of the present invention is as follows:

[0027] The low-temperature carbon dioxide gas output from the pressure stabilizing tank 1 is pressurized by the compressor 2 and then enters the recuperator 3, where it exchanges heat and is heated up with the higher-temperature exhaust gas output from the turbine generator set 5. Then it enters the boiler 4 to absorb heat and be heated up to the rated parameters. The carbon dioxide output from the boiler 4 enters the turbine generator set 5 to expand and do work to drive the generator to generate electricity. The exhaust gas discharged from the turbine generator set 5 enters the recuperator 3 to exchange heat and cool down, then enters the precooler 6 to be cooled, and then enters the pressure stabilizing tank 1 to complete the next cycle.

[0028] The working medium in the pressure stabilizing tank 1 is compressed by the compressor 2, the pressure increases, the temperature increases, then it exchanges heat and cools down with the external environment under the action of the cooling fan 7 through the thick-tube cooler 8, then enters the thin-tube refrigerator 10 through the throttle valve 9 to be further cooled, and finally is discharged through the vent pipe 12.

[0029] A drain valve 11 is provided at the drain outlet at the bottom of the pressure stabilizing tank 1. The low-temperature working medium in the capillary cooler 10 exchanges heat with the gas outside the tube. When the gas in the pressure stabilizing tank 1 encounters the capillary cooler 10, water vapor condenses into droplets, gradually drips to the bottom of the pressure stabilizing tank 1, and finally is discharged through the drain valve 11.

[0030] In the initial stage of the unit startup, the present invention operates continuously. After the unit carries a certain load, the water removal device can be set to operate regularly. If there is no water discharged from the bottom of the pressure stabilizing tank 1 for two consecutive times, it indicates that there is no moisture in the working medium, and the water removal device can be stopped.

Claims

1. A supercritical carbon dioxide power generation unit with the function of self-removing water from the working fluid, characterized in that, it includes a pressure stabilizing tank (1), a compressor (2), a recuperator (3), a boiler (4), a turbine generator set (5), a precooler (6), a cooling fan (7), a thick-tube cooler (8), a thin-tube refrigerator (10) and a drain pipe (12); The outlet of the pressure stabilizing tank (1) is divided into two paths after passing through the compressor (2). One path is connected to the inlet of the boiler (4) through the heat absorption side of the recuperator (3). The outlet of the boiler (4) is connected to the inlet of the turbine generator set (5). The exhaust port of the turbine generator set (5) is connected to the inlet of the precooler (6) through the heat release side of the recuperator (3). The outlet of the precooler (6) is connected to the inlet of the pressure stabilizing tank (1). The other path is connected to the drain pipe (12) through the thick-tube cooler (8) and the thin-tube refrigerator (10). The thin-tube refrigerator (10) is located inside the pressure stabilizing tank (1). A liquid drain port is provided at the bottom of the pressure stabilizing tank (1). The cooling fan (7) is facing the thick-tube cooler (8); The thick-tube cooler (8) is connected to the drain pipe (12) through a throttle valve (9) and the thin-tube refrigerator (10); A drain valve (11) is provided at the liquid drain port.

2. The supercritical carbon dioxide power generation unit with the function of self-removing water from the working fluid according to claim 1, characterized in that, the compressor (2) is a centrifugal compressor.

3. The supercritical carbon dioxide power generation unit with the function of self-removing water from the working fluid according to claim 1, characterized in that, the recuperator (3) is a printed circuit board heat exchanger.

4. The supercritical carbon dioxide power generation unit with the function of self-removing water from the working fluid according to claim 1, characterized in that, the precooler (6) is a printed circuit board heat exchanger.

5. The supercritical carbon dioxide power generation unit with the function of self-removing water from the working fluid according to claim 1, characterized in that, the throttle valve (9) is an electric control valve.

6. The supercritical carbon dioxide power generation unit with the function of self-removing water from the working fluid according to claim 1, characterized in that, both the thin-tube refrigerator (10) and the thick-tube cooler (8) are wound by steel pipes.

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